A radio frequency (RF) communication system typically provides wireless communication between a base station and a mobile station. The base station often has the ability to "page" or call the mobile station, whether it be to provide the mobile station with a text or voice message or to establish a two-way voice call between a user of the mobile station and a third-party caller.
One of the most important aspects of such a system is its call completion rate. A call completion rate may be defined as N.sub.D /N.sub.P, where N.sub.P is the number of paging messages sent to and intended for the mobile station, and N.sub.D is the number of successful detections of the paging messages by the mobile station. Unfortunately, some RF communication systems may have poor call completion rates due to, for example, low received signal strengths and environmental interferences.
To improve overall quality and reliability of communication, such a system may conform to a common air interface specification that specifies an error detection code and error correction codes to be sent with information data in an encoded information unit. For example, a personal digital cellular (PDC) system adheres to a communication standard issued by the Research and Development Center for Radio Systems (RCR), now known as the Association of Radio Industries and Businesses of Japan (ARIB), under the name STD-27 (RCR STD-27, 1991). This standard outlines Bose-Chaudhuri-Hocquenghem (BCH) forward error correction (FEC) codes for correcting single errors in data portions of the information data, and a cyclical redundancy check (CRC) code for detecting remaining errors in the corrected data portions.
Conventional methods of decoding such an encoded information unit, one of which is outlined generally in the RCR STD-27, include the following steps: (1) receiving an encoded information unit; (2) generating, using the BCH FEC codes, a BCH syndrome for each data portion of the encoded information unit; (3) correcting, using the BCH syndromes, single errors that may exist in each data portion to thereby generate a post-correction information unit; (4) detecting, using the CRC code, if an error exists in the post-correction information unit; (5) processing and performing a function based on the post-correction information unit if no errors are detected therein; and (6) discarding the post-correction information unit if an error is detected therein.
While such methods and standards have generally improved communication, reliability may still be less than satisfactory since post-correction information units may often have errors and therefore are discarded and unused. If a mobile station acts upon or processes such corrupted data, it will likely respond improperly with undesirable consequences.
Furthermore, some messages, such as paging messages, are sent only once to the mobile station without retransmission by the base station. Therefore, if a paging message is corrupted over a communication channel, a page to the mobile station may be missed entirely even though the mobile station is ready and available to receive calls.
Accordingly, there is an existing need for an improved method and apparatus for detecting errors and decoding and processing messages, especially one suitable for increasing call completion rates in RF communication systems.